An active vitamin D.sub.3 derivative has calcium absorption-stimulating activity in the small intestine, and activity such as the control of bone resorption and osteogenesis in the bones, and it is used as a treating agent for diseases caused by various kinds of calcium metabolism disorders. In recent years, immunoregulatory activity, cell proliferation inhibitory activity and cell differentiation inducting activity have been found besides these activities. For example, applications to a treating agent for rheumatoid arthritis (Japanese Unexamined Patent Publication No. 56-26820), an antiallergic agent (Japanese Un-examined Patent Publication No. 63-107928, English Patent Publica-tion No. 2260904(GB 2260904-A)), a treating agent for psoriasis (Japanese Unexamined Patent Publication No. 3-68009), a treating agent for diseases attributable to thromboxane A.sub.2 production (Japanese Unexamined Patent Publication No. 5-294834), a treating agent for eczema and dermatitis (Japanese Unexamined Patent Publication No. 7-291868), etc., are being studied.
On the other hand, respiratory tract infection is a disease which is established when pathogens invade getting over infection preventing mechanisms of the respiratory tract, and the treatment is mainly based on the improvement of respiratory tract clearance by using a bronchodilator, an expectorant, etc. But, in the case of acute exacerbation with infection, the main treatment is a strong antibacterial treatment against phlogogenic bacteria. However, most underlying diseases constantly becomes worse when acute exacerbation is repeated. Further, present treatments, which depends on antibacterial agents in the extreme, are under reconsideration owing to the emergence of resistant bacteria such as MRSA.
Recently, the usefulness of a low-dose long administration of erythromycin for a chronic lower airway infectious disease has been reported, and it is attracting attention. A chronic lower airway infectious disease is a generic name for bacterial infections observed in chronic bronchitis, diffuse panbronchiolitis, bronchiectasis, etc., (sometimes, it includes bronchial asthma, chronic pulmonary emphysema, pulmonary tuberculosis sequela, etc., accompanied by infection). Although these are different in the name of disease, it is known that all of the diseases take common morbid states such as purulent sputum in large amount, fatigue dyspnea and hypoxemia. Regarding the working mechanism of erythromycin, it is understood that erythromycin's function does not depend simply on its antibacterial activity, namely, erythromycin acts not on bacteria themselves but rather on inflammatory cells which accumulate on the airway accompanied by the bacteria, especially acts on neutrophils. That is, neutrophils infiltrate into tissues by the various kinds of stimulation caused by the infection to release protease as well as active oxygen, and these substances cause epithelium damage, the trouble of ciliary movement and mucosa hypersecretion to exert a bad influence upon respiratory physiological effect, and erythromycin acts on these processes. Based on such consideration, a medicine, which suppresses the pulmonary tissue infiltration of neutrophils or suppresses the activity of neutrophils, can be useful as a treating agent for inflammatory dyspnea, for example, chronic lower airway infectious disease.
Further, regarding the effect on malignant tumor cells, it has been reported that an active vitamin D.sub.3 derivative has various physiological activities such as proliferation suppression, differentiation induction and regulatory effect on immunological function. For example, it has been reported that an active vitamin derivative D.sub.3 exhibits proliferation suppressing effect or differentiation inducing effect on leukemic cells (Cancer Treatment Reports, 69, 1399-1407 (1985), and Cancer Res., 43, 5862-5867 (1983)), colon cancer cells (Gut, 33, 1660-1663 (1992), and Jpn. J. Cancer Res., 88, 1052-1062 (1997)), mammary tumor cells (Cancer Res., 53, 2534-2537 (1993), prostatic cancer cells (Endocrinology, 132, 1952-1960 (1993)), etc. In addition, regarding the occurrence of human colon cancer, there is a report on the correlation between the rate of the occurrence and the uptake of vitamin D.sub.3 (Lancet, 1, 307-309 (1985)).
Treatments of malignant tumors are important problems at therapy sites, and a number of treating agents for malignant tumors have been developed. However, most of the mechanisms of action of these treating agents are based on cell functional disorders, and serious side effects are often accompanied. Further, there is no effective treating agent for some kinds of malignant tumors. On these circumstances, the development of a treating agent for malignant tumor which exhibits a therapeutic effect based on a mechanism of action different from those of conventional treating agents and has little side effect is eagerly waited for.
Although therapeutic effects of vitamins Ds, especially active vitamin D.sub.3 and its derivatives on malignant tumors have been studied up to now (for example, Japanese Unexamined Patent Publication No. 57-149224), sufficient therapeutic effect has not been attained due to the fact that hypercalcemia, which is considered attributable to a characteristic physiological action of vitamins Ds, causes serious side effects in actual human therapy. For developing these compounds as treating agents for malignant tumors, it is therefore assumed to be effective to use compounds which do not induce hypercalcemia while keeping proliferation suppressing effect and differentiation inducing effect of vitamins Ds on the malignant tumors.